An image forming apparatus called a tandem type is known, which forms toner images on photosensitive members corresponding to the respective colors and transfers the toner images to the intermediate transfer belt in a superimposed manner, thereby generating a color image. In such an image forming apparatus, so-called color misregistration occurs when the relative positions of the toner images shift when they are superimposed.
To cope with this, Japanese Patent Laid-Open No. 7-234612 discloses forming the toner images of the respective colors for color misregistration detection on the intermediate transfer belt and detecting the relative positional shift between the toner images of the respective colors by an optical sensor, thereby performing correction.
However, since it is necessary to form the toner images for color misregistration detection on the intermediate transfer belt and further clean the formed toner images, the usability of the image forming apparatus lowers.